1. Field of the Invention
The present invention relates to a musical tone synthesizing apparatus which is suitable for synthesizing sounds of a string-striking-type instrument such as a piano.
2. Prior Art
There is a known musical tone synthesizing apparatus which activates a simulation model of a tone-generation mechanism of the non-electronic musical instrument so as to synthesize sounds of the non-electronic musical instrument. This musical tone synthesizing apparatus which synthesizes sounds of the string-striking-type instrument or a string-plucking-type instrument (e.g., guitar) has a known configuration containing a loop circuit and an excitation circuit. Herein, the loop circuit includes a delay circuit which simulates a propagation delay of vibration to be occurred on a string and a filter which simulates an acoustic loss to be occurred on a string. In addition, the excitation circuit produces and outputs an excitation signal to the loop circuit, wherein this excitation signal corresponds to an excitation vibration applied to the string when being plucked or struck. Incidentally, this kind of musical tone synthesizing apparatus is disclosed in the known documents, e.g., Japanese Patent Laid-Open Publication No. 63-40199 and Japanese Patent Publication No. 58-58679.
When synthesizing the piano sound, in order to obtain a natural sound quality, it is necessary to accurately simulate a string-striking mechanism corresponding to an excitation vibration mechanism of the piano. In order to achieve such object, we have proposed a musical tone synthesizing apparatus as disclosed in Japanese Patent Application No. 1-194580. This apparatus is designed to simulate movements of the hammer and the string to be struck based on an initial velocity applied to the hammer, an inertia mass of the hammer and an elastic characteristic of the hammer. Then, the loop circuit inputs the excitation signal corresponding to vibration velocity of the string to be struck by the hammer.
Meanwhile, hammer of the actual piano employs a felt having the elasticity and viscosity. Such viscosity affects motion of the hammer which strikes the string. For example, when the hammer collides with the string at low velocity, the hammer is partially deformed responsive to the collision. In contrast, when the hammer collides with the string at high velocity, the hammer does not follow up with the collision but it acts like a rigid body. Such phenomenon is occurred not only in the piano but also in the other non-electronic musical instruments. For example, in case of the guitar, the excitation vibration mechanism, i.e., a pick, has the viscous characteristic. Conventionally, however, there is no musical tone synthesizing apparatus which is designed under consideration of the viscous effect as described above.